Exclusive electrophysiological motor involvement in carpal tunnel syndrome

Unusual Motor Hand Neuropathies: Causes, Diagnosis, and Evaluation of Motor Impairments

Background Isolated hand motor nerve injuries, specifically those affecting the recurrent motor branch of the median nerve and the deep motor branch of the ulnar nerve, are rarely reported in medical literature. Diagnosing and quantifying these injuries pose significant challenges due to their uncommon nature and the variety of mechanisms that can cause them. Methodology This study reviews six unusual cases of isolated damage to the recurrent motor branch of the median nerve and the deep motor branch of the ulnar nerve, including cases with combined injuries. The etiologies include various traumatic and compressive mechanisms, such as a blow from the thenar to the back of a knife blade, long-distance cycling, impact from a broken shovel handle, knife injury, and damage from a screw while using a cordless screwdriver. In one case, the cause was indeterminate. Diagnostic methods involved clinical evaluation, electrophysiological testing (nerve conduction studies and electromyography), and high-resolution ultrasound imaging. A thorough medical history was also crucial in understanding the injury mechanisms. Results The cases demonstrated a range of causes for isolated hand motor nerve injuries, with both traumatic and compressive mechanisms identified. The diagnostic process highlighted the value of integrating clinical assessments, electrophysiological data, and ultrasound imaging to accurately diagnose and understand the extent and nature of the injuries. Conclusions Isolated motor nerve injuries in the hand can arise from diverse and often unexpected causes. Comprehensive clinical evaluation, supported by electrophysiological testing and ultrasound imaging, is essential for accurate diagnosis and management. A detailed medical history is invaluable in identifying the mechanism of injury, which is critical for developing an appropriate treatment plan. The study underscores the importance of a multidisciplinary approach in diagnosing and treating these rare neuropathies.

Effectiveness of an Endoscopic Recurrent Branch Release Procedure Combined with Standard Endoscopic Carpal Tunnel Release Surgery Compared to Standard Endoscopic Carpal Tunnel Release Surgery Alone: A Propensity Score-Matched Study

Background: The purpose of this study is to compare the effectiveness of endoscopic release of the recurrent branch from surrounding soft tissue in combination with standard endoscopic carpal tunnel release (ECTR) surgery to standard ECTR surgery alone in patients with established abductor pollicis brevis (APB) muscle weakness. Methods: Using propensity score matching, we compared the recovery rates of postoperative clinical symptoms in patients with idiopathic carpal tunnel syndrome in whom the preoperative Medical Research Council (MRC) scale of the APB muscle (MRC-APB) was zero (no contraction) and with undetectable distal motor latency (DML) of APB, to those who underwent standard ECTR surgery alone and those who underwent recurrent branch release in addition to standard ECTR. Results: Forty-nine hands in the recurrent branch release group and 49 hands in the standard ECTR surgery group were extracted. There were statistically significant differences in postoperative recovery rate from MRC-APB 0 to '4 or 5' at 30 months (OR: 2.42; 95% CI: 1.03-5.67; p = 0.04) and at final follow-up (OR: 2.64; 95% CI: 1.11-6.26; p = 0.03). There were statistically significant differences in postoperative recovery of MRC-APB scales at 24 months (p = 0.03), 30 months (p = 0.02) and at final follow-up (p = 0.02). There were statistically significant differences in postoperative recovery of DML (p = 0.04). Conclusions: Endoscopic release of the recurrent branch in combination with standard ECTR surgery showed better recovery rates in MRC-APB and DML recovery compared to standard ECTR surgery alone. Level of Evidence: Level III (Therapeutic).

Sustained atypical myokymia of the abductor pollicis brevis with a focal slowing of the median nerve motor axons at the wrist

OBJECTIVE

We report a case of sustained atypical myokymia associated with short bursts of neuromyotonic discharges involving the abductor pollicis brevis (APB) muscle and describe a useful way of detecting a focal slowing involving a small number of median nerve motor fibers with a concentric needle using the filter setting for single fiber electromyography (EMG).

METHODS AND RESULTS

A 62-year-old woman developed right thumb twitches at regular interval of 1.7-3.3 s (0.6-0.3 Hz), which continued for more than four months. Muscle twitches remained the same during altered hand position, psychological stress, or sleep. A concentric needle inserted in the active zone of the APB muscle revealed myokymic bursts with a characteristic of neuromyotonic discharges. Inching study, stimulating at 5 mm increment along the median nerve and recording with a concentric needle using a filter setting for single fiber EMG, revealed a focal slowing of the motor fibers at a point 5-10 mm distal from the distal crease of the wrist, an entrapment site occasionally seen in the carpal tunnel syndrome. One injection of botulinum toxin type A eliminated the myokymia, which then recurred two and a half years later, showing less prominent muscle twitches.

CONCLUSIONS

Sustained atypical myokymia seen in our case represented bursts of neuromyotonic discharges originated from a focal demyelinating lesion involving a few median nerve motor fibers.

High-resolution ultrasound visualization of the recurrent motor branch of the median nerve: normal and first pathological findings

Purpose

To evaluate in a prospective study the possibility of visualization and diagnostic assessment of the recurrent motor branch (RMB) of the median nerve with high-resolution ultrasound (HRUS).

Materials and methods

HRUS with high-frequency probes (18–22 MhZ) was used to locate the RMB in eight fresh cadaveric hands. To verify correct identification, ink-marking and consecutive dissection were performed. Measurement of the RMB maximum transverse-diameter, an evaluation of the origin from the median nerve and its course in relation to the transverse carpal ligament, was performed in both hands of ten healthy volunteers (n = 20). Cases referred for HRUS examinations for suspected RMB lesions were also assessed.

Results

The RMB was clearly visible in all anatomical specimens and all volunteers. Dissection confirmed HRUS findings in all anatomical specimens. Mean RMB diameter in volunteers was 0.7 mm ± 0.1 (range, 0.6–1). The RMB originated from the radial aspect in 11 (55%), central aspect in eight (40%) and ulnar aspect in one (5%) hand. Nineteen (95%) extraligamentous courses and one (5%) subligamentous course were detected. Three patients with visible RMB abnormalities on HRUS were identified.

Conclusion

HRUS is able to reliably visualize the RMB, its variations and pathologies.

Key Points

• Ultrasound allows visualization of the recurrent motor branch of the median nerve.

• Ultrasound may help clinicians to assess patients with recurrent motor branch pathologies.

• Patient management may become more appropriate and targeted therapy could be improved.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-016-4671-1) contains supplementary material, which is available to authorized users.

Revision Surgery after Carpal Tunnel Release –Analysis of the Pathology in 200 Cases during a 2 Year Period

Carpal tunnel release (CTR) is regarded as a common and successful operative procedure in hand surgery. However, an increasing number of patients with complications have been referred to our hospital. This retrospective investigation was undertaken to clarify the reasons for persisting or recurrent symptoms in 200 patients who underwent secondary exploration during a 26 month period at a single institution. In 108 cases, the flexor retinaculum was found to have been released incompletely. In 12 patients, a nerve laceration had occurred during the primary intervention. In 46 patients, symptoms were due to the nerve being tethered in scar tissue. The re-exploration revealed circumferential fibrosis around and within the median nerve in 17 patients and a tumour in the carpal tunnel in four patients. In 13 patients, no specific reason was found for recurrence of symptoms. We conclude that CTR seems to be a widely underestimated procedure and revision surgery could be largely avoided by reducing technical errors during the primary operation.

Relation between distal motor latency delay and sensory action potential absence of the median nerve in carpal tunnel syndrome

OBJECTIVE

To elucidate the cutoff value for distal motor latency (DML) at which sensory nerve action potentials (SNAPs) are absent in carpal tunnel syndrome (CTS) patients.

METHOD

We examined 157 hands in 129 patients with CTS retrospectively. We classified the patients according to whether SNAPs were successfully obtained. Group A consisted of hands with SNAPs, while Group B consisted of hands without SNAPs. The cutoff value for DML was determined by receiver-operating characteristic curve analysis. We enrolled 130 hands with CTS for the analysis, because measurements were successful in 130 hands for compound muscle action potentials and in 82 hands for SNAPs from a total of 157 hands investigated.

RESULTS

A significant correlation was observed between DML and SCV (P<0.0001, R*2=0.40). The most discriminative cutoff value for DML was 7.7ms, resulting in a sensitivity of 79.6% and specificity of 79.3%.

CONCLUSION

Cases in which SNAPs are evoked despite a DML longer than 7.7ms should raise suspicion.

Compression and entrapment neuropathies

Peripheral nerve entrapments are frequent. They usually appear in anatomical tunnels such as the carpal tunnel. Nerve compressions may be due to external pressure such as the fibular nerve at the fibular head. Malignant or benign tumors may also damage the nerve. For each nerve from the upper and lower limbs, detailed clinical, electrophysiological, imaging, and therapeutic aspects are described. In the upper limbs, carpal tunnel syndrome and ulnar neuropathy at the elbow are the most frequent manifestations; the radial nerve is less frequently involved. Other nerves may occasionally be damaged and these are described also. In the lower limbs, the fibular nerve is most frequently involved, usually at the fibular head by external compression. Other nerves may also be involved and are therefore described. The clinical and electrophysiological examination are very important for the diagnosis, but imaging is also of great use. Treatments available for each nerve disease are discussed.

Thenar motor neuropathy electrophysiological study of 28 cases

PURPOSE

To report an electrophysiological study on thenar motor neuropathy of the median nerve.

METHODS

Twenty-eight consecutive patients (mean age, 48.8 years; 17 men) with dominant hand thenar muscle weakness without sensory symptoms were enrolled in this study. Electromyography of hand and forearm muscles and neurography of median, ulnar, radial, and palmar nerves, including distal motor latency recording from the second interosseous-lumbrical muscles, were performed.

RESULTS

Complete denervation of the abductor pollicis brevis muscle was observed in one case and delayed median abductor pollicis brevis-distal motor latency was observed in the others. Other neurographic findings were normal.

CONCLUSIONS

Thenar motor neuropathy may have different pathogeneses. It may be considered a variant of carpal tunnel syndrome involving the motor branch only or more likely due to chronic direct compression of the branch, because it preferentially affects males, dominant hand, and persons doing manual work. In both cases, anatomic origin and variations in the course of the branch may favor thenar motor neuropathy.

Prevalent involvement of thenar motor fibres in vineyard workers with carpal tunnel syndrome

OBJECTIVE

Carpal tunnel syndrome (CTS) has a high prevalence in agricultural workers, especially those engaged in vineyards. We postulated that vineyard CTS was electrophysiologically different from CTS of other subjects. We performed a retrospective cross-sectional electrophysiological study of two cohorts of consecutive patients with CTS, the first consisting of vineyard workers and the second, of other unselected types of workers, housewives and pensioners.

METHODS

Thirty-three vineyard workers (mean age 46.8years, 42% women) and 205 patients with other occupations (mean age 53.7years; 66% women) were enrolled. All patients underwent sensory and motor neurography of the median and ulnar nerves. Differences in demographic and electrophysiological findings between groups were calculated and multiple linear regression analysis was performed to eliminate the influence of potential confounding factors (age, sex, BMI, clinical severity of CTS) on the results of univariate difference analysis.

RESULTS

Univariate analysis showed that DML was longer and compound muscle action potential amplitude of the median nerve, recorded from the abductor pollicis brevis muscle, was smaller in vineyard workers than in the other CTS patients. These differences remained significant after adjusting the results for confounding factors.

CONCLUSIONS

The vineyard workers showed a different pattern of CTS than the other patients: thenar motor fibres were more affected, presumably due to chronic compression on the thenar branch. This suggests an association between "common" CTS and thenar mononeuropathy.

SIGNIFICANCE

Occupational physiologists should clarify the mechanisms of neuromuscular engagement in particular jobs and ergonomists design suitable working tools, because many "individual" risk factors are difficult to change, but workplace-related risk factors can be modified.

Compression neuropathy of the motor fibers of the median nerve at wrist level

Selective electrophysiological involvement of median motor fibers is rare in carpal tunnel syndrome. We report a patient with compression neuropathy of the median nerve who presented with isolated motor signs and symptoms without macroscopic evidence of compressive pathologies.

A handheld nerve conduction measuring device in carpal tunnel syndrome

OBJECTIVES

The diagnostic utility and reliability of an easy-to-operate novel handheld nerve conduction tester in carpal tunnel syndrome (CTS) were evaluated.

MATERIALS AND METHODS

Using the test device, the sensory nerve conductions (SNC) in the median and ulnar nerves were compared with each other in 194 patients with suspected CTS and 95 healthy controls. The test device results were compared with the results of nerve conduction studies (NCS) with traditional instrumentation.

RESULTS

The new device correctly classified 145 of the 149 hands (97.3%) without median nerve lesion and 171 of the 200 hands (85.5%) with median nerve lesions in traditional NCS. The specificity of the new tester compared with traditional instrumentation was 98%. The correlation coefficient for different technicians in different studies was 0.87.

CONCLUSIONS

The findings obtained with the new tester in CTS were reliable and reproducible. This tester may increase availability of NCS in CTS.

Sensory-motor index is useful parameter in electroneurographical diagnosis of carpal tunnel syndrome

It was performed electroneurographic (ENG) studies with surface electrodes and examined nervus medianus (NM) in 60 patients (38 females), average age of 50,28 years (X+/-SD=50,28+/-11), with clinical diagnosis of carpal tunnel syndrome (CTS) and at least one border or discrete abnormal value of conventional electrophysiological tests. It was also examined 57 healthy individuals (33 females) as control group, average age of 45,65 years (X+/-SD=45,65+/-9,68). The sensitivity and specificity of sensory-motor index (SMI), terminal latency index (TLI) and residual latency (RL) were calculated and compared. SMI is determinate by using following formula: distal distance (DD) (in cm)/distal motor latency (DML) (in ms) + sensory conduction velocity (SCV) (in m/s)/motor conduction velocity (MCV) (in m/s) of NM. SCV of NM was measured by antidromic technique in segment wrist-index finger and MCV of NM in forearm segment above wrist. SMI mean value of control group was 3,45 (X+/-SD=3,45+/-0,45) with lower limit of normal value 2,82 and in patients with CTS 2,13 (X+/-SD=2,13 +/-0,37). The sensitivity of SMI in patients with CTS was 98,51%. SMI is useful parameter in electroneurographical diagnosis of CTS and it's determination is easy and fast and specially important in cases with border or discrete abnormal values of other NM electrophysiological parameters, when SMI values can indicate incipient phase of CTS evolution. In rare cases (about 1%) of CTS with selective NM motor axons affection, SMI may have normal value (false negative result), but DML is always prolonged in this cases. SMI is not dependent on age and DD values in patients with CTS and control subjects.

Factors influencing F-wave latency detection of lumbosacral root lesions using a detection theory based model

OBJECTIVE

To evaluate the F-wave dilution hypothesis; which implies that absolute F-wave latencies obscure the much smaller delay associated with slow intra-lesion conduction, such is caused by nerve root compression in lumbosacral radiculopathy. A corollary objective is to determine how F-wave measurement and pathological factors influence diagnostic accuracy.

METHODS

An analytical model is developed based on signal detection theory and a number of simplifying assumptions. Diagnostic accuracy, quantified by the area under the receiver operating characteristic (ROC) curve, is determined for various model realizations derived from the clinical and experimental neurophysiology literature. A preliminary experimental validation of model predictions is also performed.

RESULTS

Absolute F-wave latency does not influence the accuracy of focal lesion detection. F-wave latency variance and lesion pathology are the determinant factors. F-wave latencies and distal latencies are estimated to have qualitatively similar detection characteristics, although distal latencies have quantitatively better diagnostic efficacy for comparable focal pathology. Preliminary experimental results support the modeled dependence of diagnostic accuracy on latency variance and lesion severity.

CONCLUSIONS

Absolute F-wave latency does not dilute slow conduction within focal lesions, such as in lumbosacral radiculopathy. The dominant measurement factor is F-wave latency variance.

SIGNIFICANCE

To maximize the diagnostic utility of F-wave latencies, focus must be placed on reducing latency variance, such as through correction for demographic covariates. This model calls into question the F-wave dilution hypothesis.

Spread of the radial SNAP: A pitfall in the diagnosis of carpal tunnel syndrome using standard orthodromic sensory conduction study

OBJECTIVE

To investigate the occurrence of the spread of the radial sensory nerve action potential (SNAP) among patients with carpal tunnel syndrome (CTS) during standard median orthodromic sensory conduction study (SCS) using index finger stimulation.

METHODS

We prospectively examined 74 hands in 56 CTS patients. We stimulated the index finger using ring electrodes. SNAPs were recorded at wrist over median and radial nerves.

RESULTS

A spread of radial SNAP was clearly identified over the median nerve despite its small amplitude, in 72/74 hands during stimulation of the base of the index finger. In hands with delayed median SNAP, two peaks were observed; however in hands with absence of genuine median SNAP, only one peak of the spread was noticed. The proximal interphalangeal joint (PIP) stimulation still elicited an identifiable spread in 47/74 hands.

CONCLUSION

This spread phenomenon is a previously undescribed pitfall during the standard median orthodromic SCS, frequently occurring in CTS patients.

SIGNIFICANCE

In severe CTS cases, one may make wrong conclusion of normal median sensory latency if unaware of this pitfall.